Find electric field (in $N/C$) at point $P$ in vector form due to point charges kept as shown (Here charge $Q=0.25 \mu C$)

$$\begin{gathered} \overrightarrow{r_1}=\left(3-0\right)\hat{i}+\left(0-4\right)\hat{j}+\left(0-0\right)\hat{k} \\ \overrightarrow{r_1}=3\hat{i}-4\hat{j}and r_1=\sqrt{3^2+4^2}=5 \\ \overrightarrow{r_2}=\left(3-0\right)\hat{i}+\left(0-0\right)\hat{j}+\left(0-4\right)\hat{k} \\ \overrightarrow{r_2}=3\hat{i}-4\hat{k} and r_2=\sqrt{3^2+4^2}=5 \end{gathered}$$

$$\begin{gathered} \overrightarrow{E_1}=k\frac{Q}{r_1^2}\widehat{r_1}=\left(9\times {10}^9\right)\frac{\left(25\times {10}^{-8}\right)}{5^2}\frac{\left(3\hat{i}-4\hat{j}\right)}{5} \\ =18\left(3\hat{i}-4\hat{j}\right)=54\hat{i}-72\hat{j} N/C \\ Similarly, \overrightarrow{E_2}=\frac{kQ}{r_2^2}\widehat{r_2}=\left(9\times {10}^9\right)\frac{\left(25\times {10}^{-8}\right)}{5^2}\frac{\left(3\hat{i}-4\hat{k}\right)}{5} \\ =18\left(3\hat{i}-4\hat{k}\right)=54\hat{i}-72\hat{k} N/C \end{gathered}$$

Net field at $$\begin{gathered} P, \overrightarrow{E}=\overrightarrow{E_1}+\overrightarrow{E_2}=\left(54\hat{i}-72\hat{j}\right)+\left(54\hat{i}-72\hat{k}\right) \\ =108\hat{i}-72\hat{j}-72\hat{k} \end{gathered}$$